Portable electronic devices, such as those configured to be handheld or otherwise associated with a user, are employed in a wide variety of applications and environments. The ubiquity of such devices as mobile phones, wearables, including smart watches and glasses, digital still cameras and video cameras, handheld music and media players, portable video game devices and controllers, tablets, mobile internet devices (MIDs), personal navigation devices (PNDs), other APPlication acCESSORIES (or Appcessories for short) and other similar devices speaks the popularity and desire for these types of devices. Increasingly, such devices are equipped with one or more sensors or other systems for determining the position or motion of the portable device with increasing sophistication and accuracy. Likewise, additional sensing capabilities are commonly available in the form of proximity and ambient light sensors, image sensors, barometers, magnetometers and the like. Still further, such portable devices often feature navigation systems, such as a Global Navigation Satellite Systems (GNSS), that enable precise determinations regarding geophysical position and movement. Corresponding advances in computation power, size, power consumption and prices make such portable devices powerful computing tools with extensive capabilities to detect their environment.
Given the noted popularity in portable devices having some or all of these capabilities, a wide variety of sensor data may be available and therefore leveraged to obtain useful information concerning activities in which the user may be engaged. One significant application relates to position or orientation determinations made in relation to given venue or location of the user. Generally, such applications may involve providing a navigation solution for the user of the portable device. A navigation solution may benefit the user by helping them find a desired location or to reconstruct a trajectory. However, a navigation solution may also be employed for other purposes, such as consumer analytics. As will be appreciated, the trajectory of a user through a retail venue may give a wide variety of useful information, including identifying items in which the user may be interested or evaluating characteristics of the retail experience that may be used to optimize store layout or shopping efficiency.
One technique for determining information regarding the positioning of an individual, whether in a moving vehicle or on foot, is commonly achieved using known reference-based systems, such as the Global Navigation Satellite Systems (GNSS). The GNSS comprises a group of satellites that transmit encoded signals to receivers on the ground that, by means of trilateration techniques, can calculate their position using the travel time of the satellites' signals and information about the satellites' current location. Such positioning techniques are also commonly utilized to position a device (such as for example, among others, a mobile phone) within or on the moving platform, whether such device is tethered or non-tethered to the moving platform. Currently, the most popular form of GNSS for obtaining absolute position measurements is the global positioning system (GPS), which is capable of providing accurate position and velocity information provided that there is sufficient satellite coverage. However, where the satellite signal becomes disrupted or blocked such as, for example, in urban settings, tunnels and other GNSS-degraded or GNSS-denied environments, a degradation or interruption or “gap” in the GPS positioning information can result.
In order to achieve more accurate, consistent and uninterrupted positioning information, alternative sources of positioning information may be self-contained and/or “non-reference based” systems within the device or the platform, and thus need not depend upon external sources of information that can become interrupted or blocked. One such “non-reference based” or relative positioning system is the inertial navigation system (INS), inertial sensors are self-contained sensors within the device or platform that use gyroscopes to measure rate of rotation/angle, and accelerometers to measure specific force (from which acceleration is obtained). Using initial estimates of position, velocity and orientation angles of the device or platform as a starting point, the INS readings can subsequently be integrated over time and used to determine the current position, velocity and orientation angles of the device and its relative misalignment within the platform. Typically, measurements are integrated once for gyroscopes to yield orientation angles and twice for accelerometers to yield position of the device or platform incorporating the orientation angles. Thus, the measurements of gyroscopes will undergo a triple integration operation during the process of yielding position.
A navigation solution based on dead reckoning from inertial sensors alone, however, may suffer because the required integration operations of data results in positioning solutions that drift with time, thereby leading to an unbounded accumulation of errors. Further problems in providing accurate position or navigation information about a portable device can arise where the device is capable of moving freely (e.g. without any constraints) or can move with some constraints within the moving platform. Inaccuracies can arise in such cases because the coordinate frame of the inertial sensors (accelerometers and gyroscopes) of the device is not aligned with the coordinate frame of the moving platform. The device and the moving platform can be misaligned with respect to one another, and such misalignment can change over time. For example, where the device moves freely without constraint, the misalignment of the device and the platform can change without constraint. Where the device is capable of constrained movement, the misalignment of the device and the platform can also change, wherein the change is subject to constraints. Where the portable device is mounted within the platform, there may still be a misalignment where such mounting results in a misalignment between the coordinate frame of the device and the coordinate frame of the platform (although such misalignment would not change over time). It should be noted that a skilled person would know and understand that the misalignment between a portable device and a moving platform does not equate or relate to misalignment that might occur where a navigation module for positioning a moving platform is positioned incorrectly within the moving platform, thereby resulting in a misalignment between the module and the moving platform.
To help compensate for these noted deficiencies of inertial sensors, dead reckoning strategies may attempt to characterize aspects of motion that may be due to the mode of motion being employed by the user. For example, pedestrian dead reckoning may involve estimating the number of steps taken and step length in order to supplement the information obtained from inertial sensors when developing a navigation solution. A similar example may occur when the user is pushing, pulling or otherwise propelling an apparatus through on foot motion, as opposed to a pedal-powered vehicle such as a bicycle or an independently-powered vehicle such as a car. Cart is defined as any apparatus that is propelled by on foot motion of a user, so it can be pushed or pulled by a user. The portable device is being conveyed by the cart. Some examples are given herein for demonstration. In one example, a user in a retail shopping venue may have a shopping cart or other similar wheeled vehicle that may be used to hold goods as they are selected for purchase. The user may elect to place the portable device within the cart, either loosely on a surface of the cart or in a holder that may or may not be adapted to that purpose. For example, it is common practice for a user to place their portable device within a cupholder or other similar structure. As discussed above, these usages lead to situations in which the portable device may or may not be constrained within the cart (i.e., the platform), with the resulting possibility that the relative orientation of the portable device with respect to the cart may not be known ahead of time or may change at any moment. As a further example, the portable device may be contained within another object, such as a purse, backpack, briefcase, bag or any other similar item, and the other containing object is then associated with the cart. When the containing object is simply placed within the cart, the conditions may be similar to those in which the portable device alone is place within the cart. However, the containing object may be hung from a handle or hook of the cart, allowing it to swing to varying degrees, which may impart an additional motion component that will be measured by the inertial sensors. In all those cases, the portable device is conveyed by the cart.
Although one example of a cart is a shopping cart, there are several other examples of carts. Among these other examples are child-carrying devices or strollers. One of ordinary skill in the art will appreciate that similar conditions may exist in applications involving other pedestrian-powered vehicles or on-foot user-powered vehicles or apparatus. Further, even though the vehicle typically may be wheeled, other types of vehicles, such as a sled that travels on skids or other sliding surfaces, may also have similar characteristics as long as the vehicle is propelled by on-foot motion of the user. For the purposes of this disclosure, any such pedestrian-propelled vehicle is a cart. More broadly, a portable device may be contained within or otherwise associated with a vehicle that is propelled, pushed or pulled, by the motion of a pedestrian, be it walking, running or other types of on foot motion. The techniques of this disclosure are directed to processing the sensor data from a portable device in such an application to provide a navigation solution.